Number 4 - Jordan Journal of Biological Sciences

More documents

Recommendations

Info

144 © 2010 Jordan Journal of Biological Sciences. All rights reserved - Volume 3, Number 4 Female fish was exposed to three lethal concentrations of selenium and its compounds. The three lethal concentration of selenium chosen were 2, 5 and 10 mg/l and the response to oxygen uptake was studied. There was a uniform decrease in oxygen utilization at the lowest dose of 2 mg/l, percent utilization fluctuated between 59.01% and 62.24%. At 5 mg/l, the rate of uptake was drastically affected and a slow recovery in uptake with increase in exposure period was observed. Fish after exposure to 10 mg/l showed initial increase in uptake, which decreased gradually from 18.03% to 13.69% (at 72 hr) and later recovery in uptake of 40% was observed at 96 hr of exposure. Data revealed that first two days of exposure, percent uptake was not found to be concentration – dependent and decrease in last two days of uptake was concentration – dependent. In response to selenite exposure (2, 5 and 10 mg/l), fish did not show uniform consumption of oxygen however the uptake rate fluctuated with time of exposure and concentration selenite concentration. Lower concentration of selenite showed initial increase in uptake fallowed by sharp decline to 2.61% and in subsequent observation an enhancement fallowed by decline in uptake was noticed. Similar trend in uptake was observed at 5 and 10 mg/l of selenite. The results were statistically analyzed with Two way ANOVA and the results were statistically significant at P0.005 at exposure period. The pattern of variation in oxygen uptake in fish on exposure to three different concentrations of 5, 10 and 15 mg/l selenate showed a different trend. Fish dosed with 5 mg/l showed rapid increase in uptake at 24 hr. Thereafter there was a steep decline and later uniform pattern in uptake was observed through out the experimental period. Oxygen uptake reduced from 46.67% to 18.42% at 72 hr, followed by recovery in uptake of 28.81% at 96 hr. At higher concentration of 15 mg/l fish consumed 35.29% oxygen at 24 hr, which dropped to 3.88%, thereafter steady increase in uptake was observed. Results were statistically analyzed by two way ANOVA and were found to be significant at P0.0054. Results are presented in table 2 and Fig 2. 4. Discussion The results of the present study show that fish under toxic stress to different forms of selenium altered oxygen uptake. In general, initial decrease of oxygen uptake followed by an increase in its consumption was observed. All forms of Se have shown inhibitory action on rate of oxygen utilization and at time irregular uptake was noticed. However, as exposure period advanced a slight recovery was found in both male and female fish (Koti, 1996) has shown that Cu, Zn and Ni during lethal and sub lethal exposure (Individual and mixture of metals) altered oxygen consumption in both sexes of G.affinis. It was observed that fish in response to metal exposure secreted mucus in the test medium and red patches appeared at gill region and basal part of pectoral fins. Environmental factors such as temperature, pH, and hardness of the test medium, have shown cumulative effect on oxygen uptake of G.affinis in the presence of Cu, Zn and Ni (Kallangoudar and Patil, 1997). Lemly (1993) demonstrated metabolic stress in bluegills Lepomis macrochirus due to elevated concentration of selenium. He also showed reduced respiratory activity with increase in respiratory demand and oxygen consumption due to gill damage. According to (Tovell et al., 1975) metals mainly enter fish through respiratory system. The mechanism for metal uptake through gill probably occur through pores by simple diffusion (Bryan, 1979) these metals are then absorbed through cell membranes (Opperhuizen et al.,1985) Metals then coagulate in protoplasm after absorption into the bodies of aquatic animals (Skidmore, 1964). The decrease in oxygen uptake observed following exposure to selenium, selenite and selenate was possibly due to mucus precipitation on gills, during the present study mucus was present on the gills which appeared as reddish patches and was possibly secreted in response to the irritation caused by metalloids (Carpenter, 1930) investigated lethal action of dissolved metals salts on fish leading to death. According to him death resulted from interaction between metallic ions and mucus secreted by the gills and not from internal poisoning. A layer of coagulated mucus is formed on the gill surface which impairs respiratory efficiency to such an extent that fish becomes asphyxiated (Rani and Ramamurthi, 1987; Gosh and Chakraborti, 1990). Increased utilization of oxygen during later part of lethal exposure to selenium and its forms indicate that under stress fish might have used more oxygen to meet metabolic demand. Similar effect of metal stress on respiratory activity in other fish has been reported, (Davis, 1975; Van Resburg1989; Shivraj, 1990; Koti, 1996; Vijayamohanan et al., 2000). Other possible alternate reason of inhibitory action of pollutants include gill damage (Natarajan, 1981; Koti, 1996) and internal action of pollutants (Natarajan, 1981; Tuurala and Soivio, 1982) Selenium and its compounds has shown to affect oxygen uptake in both male and female fish after exposure to lethal dose, which is evident from the gradual decline in uptake at lower concentration and fluctuations at higher concentration. Which may be due to over secretion of mucus resulting in blocking of gills or due to onset of severe hyoxia, which alter the metabolic pathways or due to damage caused my metals to gill. Increase in uptake may be due to increase in demand under toxicant stress.
© 2010 Jordan Journal of Biological Sciences. All rights reserved - Volume 3, Number 4 Table 1. Percent oxygen uptake in male fish G.affinis after exposure to lethal concentration of selenium and its salts. Toxicant Dose( mg/l) Control - Exposure period ( hours) 24 48 72 96 39.57±0.86 (100%) 35.25±0.96 (100%) 22.62±1.16 (100%) 18.69±1.28 (100%) F-Ratio P-value - - Se 5 36.70±0.48 15.74±0.44 50.21±0.57 59.39±0.53 0.530 0.001 6 5.06±0.73 -62 .96±1.53 18.02±0.93 21.80±1.02 6.630 0.001 10 20.88±0.61 -76.85±0.93 -3.43±1.18 12.40±1.14 5.570 0.001 selenite 8 28.36±0.51 45.59±0.53 57.44±0.50 59.76±0.52 70.260 0.001 9.5 23.40±0.56 42.40±0.57 61.27±0.45 55.85±0.59 7.610 0.001 13 7.09±0.65 37.17±0.60 53.19±0.57 53.12±0.61 52.220 0.001 selenate 65 32.74±0.60 32.96±0.65 55.08±0.55 61.68±0.50 186.854 0.001 75 15.20±0.73 7.85±0.87 19.49±0.94 31.03±0.89 25.504 0.001 85 2.92±0.81 5.75±0.90 6.77±1.08 29.88±0.90 12.914 0.001 Results are Significant at P
Page 2 and 3: INSTRUCTIONS FOR AUTHORS All submit
Page 4 and 5: Informed Consent: All manuscripts r
Page 7: JJBS Jordan Journal of Biological S
Page 10 and 11: 134 © 2010 Jordan Journal of Biolo
Page 17 and 18: JJBS Jordan Journal of Biological S
Page 19: © 2010 Jordan Journal of Biologica
Page 25 and 26: © 2010 Jordan Journal of Biologica
Page 38 and 39: 162 Oithona oculata O. attenuata O.
Page 70 and 71:
194 © 2010 Jordan Journal of Biolo
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
show all

Number 4 - Jordan Journal of Biological Sciences

Create successful ePaper yourself

Delete template?

Save as template?